It also helps to eliminate bugs caused by forgetting to cast the value from a
string to a number, and it automatically handles rounding and clamping of
values. Plus, there’s some pretty neat new methods for dealing with unit
conversions, arithmetic and equality.

Eric has a great post with several demos and examples in his
explainer.

Async Clipboard API

const successful = document.execCommand('copy');

Synchronous copy & paste using document.execCommand can be OK for small
bits of text, but for anything else, there’s a good chance it’s synchronous
nature will block the page, causing a poor experience for the user. And the
permission model between browsers is inconsistent.

The new Async Clipboard API is a replacement that works asynchronously, and
integrates with the permission API to provide a better experience for users.

Check out Jason’s post and demos in the
explainer.
He’s also got examples that use async functions.

New Canvas Context BitmapRenderer

The canvas element lets you manipulate graphics at the pixel level, you
can draw graphs, manipulate photos, or even do real time video processing.
But, unless you’re starting with a blank canvas, you need a way to render
an image on the canvas.

Historically, that’s meant creating an image tag, then rendering it’s
contents on to the canvas. Unfortunately that means the browser needs to
store multiple copies of the image in memory.

Starting in Chrome 66, there’s a new asynchronous rendering context that’s
streamlined the display of ImageBitmap objects. They now render more
efficiently and with less jank by working asynchronously and avoiding memory
duplication.

To use it:

Call createImageBitmap and hand it an image blob, to create the image.

AudioWorklet

Worklets are in! PaintWorklet shipped in Chrome 65, and now we’re enabling
AudioWorklet
by default in Chrome 66. This new type of Worklet can be used to process
audio in the dedicated audio thread, replacing the legacy ScriptProcessorNode
which ran on the main thread. Each AudioWorklet runs in its own global scope,
reducing latency and increasing throughput stability.